1. Field of the Invention
The present invention relates to a thermoplastic tray for mixing two products A and B at the time of use. The invention is most particularly suited to mixing hair-coloring products comprising a coloring agent and an oxidizing agent.
2. Description of the Related Art
In the field of hair coloring, use is made of a coloring agent and of an oxidizing agent which are packaged separately so that their properties are not affected, and which are mixed just prior to use. For products which are of a liquid consistency, there are mixers of a type with two compartments separated by a removable stopper. Actuating means expel the stopper prior to use in order to enable the coloring agent and the oxidizing agent to be mixed. Such devices are described in European patent no. 333,541 and in U.S. Pat. No. 1,275,315. These devices are often complicated and of a relatively high cost. Furthermore, they are particularly unsuitable when one or both of the components are in cream or powder form.
Still in the field of hair coloring, it is known to package such products inside two separate compartments. Prior to use, the user opens the first compartment and, after having opened the second compartment, pours the contents of the first compartment into the second and mixes them using a spatula, for example. Generally speaking, the two compartments are totally separate from each other, i.e,. they are not joined to each other. One of the problems with this type of product is linked to the handling of the container whose contents have to be added to the contents of the other container. Because of the highly unstable nature of the products, particularly when in contact with the air, it is necessary to fill them to maximum level in order to substantially eliminate any volume of air between the free surface of the product and the sealing cover. After opening, handling therefore becomes very awkward, owing to the risk of dropping some of the product. Furthermore, when the contents of the first container are poured into the second, particularly in the case of a liquid product, if the shape of the edge of the first container is not chosen suitably, a so-called "teapot" effect may arise during pouring, resulting in an inopportune flow of liquid along the edge of the first container, which, unless special precautions are taken, will flow outside the second container. Some of the product will thus be lost which, besides wastage and environmental pollution, may result in coloring of lower quality on account of the modification in the respective measured amounts of coloring agent and oxidizing agent.
In a completely different field, namely the foodstuffs field, it is known to produce a box which includes a base on which a lid is articulated. Such a box is described in French patent application FR-A-2,731,412. The hinge described for producing this box is sufficiently rigid to permit only a simple pivoting movement between the lid and the base. In fact, since the only function of the lid is to close off the opening of the receptacle in a removable manner, the only movement needed to produce this function is a pivoting movement, insofar as the lid in the open position has its base raised above the base of the receptacle containing the product. An articulation allowing a movement which includes other components would not satisfactorily guarantee this opening and closing function. On the other hand, owing to the single pivoting movement it allows, an articulation zone of this type could never be used for the articulation of a first container with a second whose contents have to be poured into the first container.